Power operated nailing machines are in wide use in many industrial nailing applications Such nailing machines usually incorporate a pneumatic power cylinder, and a strip of nails, the nails being fed one by one under a power operated driver operated by the cylinder.
Nails can be inserted by driver strokes at great speed. This greatly reduces the time which would otherwise be required if such nails were hammered in manually
The design of a suitable nailing strip for use in such machines presents a number of different problems. Generally speaking, the strip should be of a certain desired length, and in some cases should be adapted to coil, for insertion into a larger magazine. The strip should be sufficiently strong to withstand a certain amount of abuse on the worksite and also in shipping and packaging.
The junction between the nails should preferably be such that it can easily be broken by the operation of the plunger, without interfering with the operation of the nailing machine.
In addition to all these requirements, however, the fastening system should be such that it is adaptable to nails of different types having different nail heads.
In the past, it has been proposed to fasten the nails together by adhesives, by hot melt thermoplastic materials, and by strips of adhesively bonded tape, and by welding the nails to lengths of wire.
Adhesively bonding the nails together will work only where the nails can lie side by side in contact with each other. Such a nailing strip would then be somewhat similar to a strip of wire staples for example. Thus, in the past where nailing strips were formed by simply bonding the nails together with adhesive, it was usually the practise to form modified heads on the nails having the shape of a simple "T". Nails of this type are not completely satisfactory for all industrial applications since they have a lesser holding power than nails with conventional heads.
In addition, however, the adhesive bonding was, relatively speaking, fragile. As a result, the bond was quite easily broken in handling
In an effort to overcome these problems, it has been proposed to bond the nails together with a hot melt thermo-plastic material This material is more suitable for bonding nails which are spaced apart, and are thus not in contact with one another. It is thus possible to bond nails together, where the nails are held apart from one another due to the shape of the head.
Again, however, in this case certain other problems arose. A firm plastic material was easily shattered by the impact of the plunger. A more flexible plastic material sticks to the parts and would accumulate in the nailing machine and eventually lead to a malfunction.
Attempts to secure nails using adhesive tape have also resulted in similar problems.
It has been proposed to secure nails in a strip, by welding them to two parallel lengths of wire. Such a system would have many advantages. Nails could be secured regardless of their head configuration, since they could be secured to the wire at various spacings along the wire.
Such wire, even though quite thin, is strong enough to withstand almost all shocks in handling, and thus the wastage of nails was reduced to a minimum. In addition, the design of the plunger in the nailing machine was such that it would break away the wire, carrying short lengths of wire with each nail which would then be either ripped off or driven into the wooden work piece. In neither case was there any serious problem created in the operation of the nailing machine itself.
In this case, however, there have been practical difficulties in the design and operation of the apparatus for assembling the nails into a strip and welding them to the wires.
As mentioned, the configuration of the nail head may vary according to the design of the nailing machine and according to the end use for which the nails are intended. Nails with an irregular or cut out shape in the head, can be assembled closer together in a strip. However, they must be welded to the wire in a uniform orientation, to ensure correct spacing and feeding to the plunger
Any machine for welding nails to wire must therefore arrange the nails and feed them to the welding station in precisely spaced relation
It is necessary to have some form of collating and indexing mechanism for sorting the nails, and arranging them in a strip with their nail heads in the correct orientation.
In the past, this has been a problem. Such collators were frequently liable to jam, when using nail heads with irregular shapes. In addition, they were not always 100% effective, and consequently some nails would be assembled in the strip in the wrong orientation. This would then lead to jamming of the nailing gun itself.